Grease compositions



Patented Feb. 17,

caress comrosmons John C. Zimmer, Union, and Arnold J. Moi-way, Clark Township, Union County, N. ,L, assignors to Standard Oil Development Company, a cor poration of Delaware No Drawing. Application December 30, 1944,

Serial No. 570,784

9 Claims.

The present invention relates to the field of greases, and more particularly to improvements in low temperature greases. In the usual methods of manufacturing low temperature greases, low boiling mineral oil fractions with resultant low flash points and low viscosities are compounded with metallic soaps to form plastic masses, or semi-solid grease compositions. It has been observed that the torque necessary to turn a bearing lubricated by grease is directly proportional to the viscosity of the oil used in the grease at the particular temperature. Therefore it has been necessary in the manufacture of low temperature greases to use low boiling mineral oil fractions since these fractions have low voscosities at extremely low temperatures (-100 F.) However, since the equipment, for instance the shutter on an aerial reconnaissance camera, on which this grease is to be used may at times be subjected to relatively high temperatures (150 F.) the low boiling fractions used in making the grease are limited to those which are not too volatile. The use of extremely low boiling mineral oil fractions in the manufacture of low temperature greases is therefore subject to drastic restrictions because of the high volatility of such fractions and also their use creates operational difficulties during manufacture in the nature of fire hazards. Also after the lubricant has been subjected to high temperatures, loss by volatility may result in a product which is deficient in low temperature characteristics when again used at low temperature if not relubricated.

It has now been found that the esters of allphatic dibasic acids, particularly those esters in which the esterifying radical is a branched chain alkyl radical, may be substituted for low boiling mineral oil fractions in the production of low temperature greases. These esters possess unusually high boiling points and resulting low vapor'pressures at ambient temperatures, high viscosity indices, or low viscosity-temperature coeflicient, extremely low pour points and are relatively stable chemically. Among the aliphatic dicarboxylic acids suitable for the preparation of the esters used in making the grease compositions of the present invention there may be mentioned malonic, succinic, isosuccinic, glutaric, ethyl maonic, pyro tartaric, adipic, pimelic, su-

beric, azelaic and sebacic acids. Instead of one of the enumerated acids, any acid or mixture of acids having the formula HOOCR) COOH, where R is a bivalent aliphatic hydrocarbon radicalfor example synthetic acids produced by polymerization or dimerization of unsaturated fatty acids or their estersmay be used. The esters.

which may be used in making the grease compositions of the present invention have the general formula COORi-R-COOR2, where R is a bivalent aliphatic hydrocarbon radical such as methylene, polymethylene, ethylidene, propylidene, methyl dimethylene, butenylidene and the like; R1 and R2 are hydrocarbon radicals such as branched chain alkyl, alkaryi and cyclo alkyl radicals of which secondary butyl, benzyl, cyclo hexanol and secondary octyl phenyl are representative: Isobutyl, 2-ethyl hexyi sebacate is an example of a mixed ester. These esters may contain additional constituents or functional groups such as Cl, Br, NHa, NHR, NRIRI, CHO, CO, SH, SR, RSSR, ROR, ROMetal, The esters may be made by any of the methods for producing esters known to the art.

A suitable low temperature grease composition may comprise di-2-ethyl hexyl sebacate and disecondary butyl sebacate; with from 6 to 30% of a soap of a metal selected from the group consisting of alkali and alkaline earth metals together with a stabilizer consisting of an amphoteric metal compound, specifically an oxide carbonate or soap of zinc or aluminum. As further examples, the composition may consist of a major proportion, for example 65% or more, of disecondary butyl adipate and di-isopropyl sebacate with 6 to 30% of soap and stabilizer as recited above.

One suitable method consists of reacting the alcohol with the acid at elevated temperatures in the presence of an esterification catalyst such as sulfuric acid, sulfosalicyclic acid, etc. tion is facilitated by a continuous removal of water formed during the reaction by azeotropic distillation with a solvent such as benzene, toluene, etc. or by passing inert gas through the reaction mixture to remove water of reaction. The product is washed with dilute alkali to remove the catalyst and any traces of unreacted acid and if necessary is heated under reduced pressure with or without blowing with an inert gas to remove any unreacted alcohol or other low boiling material. If necessary the product can be claytreated, and it is desirable although not absolutely necessary, that the finished ester have a neutralization number not higher than about 0.2 mg. KOH per gram of ester to obtain suitable stability-to oxidation, since free acids left in the finished material can catalyze oxidation of the product, particularly in the presence of materials such as copper or brass at elevated temperatures. Typical esters together with some of their more The reac- 3 slhgrlaiflcant properties are given in the following completely melted. The grease was then rapidly cooledbyrunningitover adrumchiller. Itia Tm: I

Oentistoksl Viscosity atllopeon ASTM with? Visa run Poor 2 m, i fi Name of later m In e o n nor. 100' r. -00' r. r. 00 W" DI See. our l Bebaca 100 0. 4: :00 am no pm thylhcxyl 80M. 3.3! mu 1m 0.101 m g: :3 Di-undoeanyl Scbacaie 4. 06 22- 8 0000 0. H0 138, 6 -80 D-2-ethylberyl alkylsied Sucnote are cm 200.000 our cat -0s Dl-Zethylhexyl Aaelate .0 0.00 n. as m0 0. m 141 no -00 100 I Extrapolaied from the 100 and 210' I. nines.

It is readily apparent from the foregoing data that esters of this type possess ideal properties with regard to pour point, viscosity and viscositytemperature characteristics, flash and boiling points necessary to minimize evaporation, making valuable lubricants for use as low temperature reases.

In making the greases of the present'invention it is preferred to make the soap first, as for instance tallow, stearic acid or hydrogenated fish oil acids are reacted with alkali until an indicator shows the alkali to be present in slight excess. The soap thus formed is dried and if desired it may be powdered to facilitate solution in the ester. 0n the other hand the soap may in case of lithium, calcium, magnesium, or aluminum be prepared by precipitation from water by pro- .cedures well established in the art. The required amount of soap is then added to the ester and the mixture heated to from 380-400 F. until the soap is completely melted in the ester. Any of the alkalis or alkaline earth metals such as sodium or calcium, magnesium, strontium, lithium being preferred, may be used for neutralizing or saponifying the soap stock. As for the soap stock. any of the ordinary higher fatty acids or the fats from which they are derived such as stearic acid. oleic, erucic, lauric, palmitic acid, tallow, lard oil. animal fats, eta, although it is preferred to use the acid derived from hydrogenated fish oil, may be used to form the soaps with which to make the grease. On formulating the greases of the present invention they will contain in general alkali or alkaline earth soaps ranging from 6-30% of the total composition, 65-93.5% of the ester or mixture of several esters. and .5-5% of a stabilizer. The use of a stabilizer smooths out the texture of the grease and-further aids in the actual production of the grease. The oxides, carbonates, or soaps of metals forming amphoteric oxides such as the soaps of zinc, tin and aluminum, have been found to be very beneficial in their use as stabilizers, particularly in the case of greases containing free alkali. Mixtures of these soaps may also be used, a particularly effective combination being 5% aluminum stearate and .5% zinc naphthenate.

The following specific example will serve to illustrate the invention in more detail.

The soaps and the esters were mixed together and heated to 360-400 F. until the soap had Tsar: II

Bleeding and evaporation tests at 180 F.

fill-Ball Bearing Conrad ype Cone Evaporation Evaporation Percent It will be noted that the usual type low temperature greases in use today are represented by grease 1. Thus around -70i F. the drag on the bearing is excessive. Greases 2 and 3 while having excellent low temperature properties are not desirable due to their excessive rate of evaporation of the low boiling constituents in the greases. For example a. bearing lubricated with grease 2 or 3 may be subjected to ground temperatures of to F. Due to excessive evaporation, the

grease left in these bearings may not again be a suitable low temperature lubricant. Grease represented by Examples 4 and 5 have excellent low temperature properties and also due to the high boiling esters used in their preparation are exceptionally stable at extremely high ground temperatures.

Tsar: III

Plasticity number (gram cm. seconds) Composition of the above greases (1) Low your coastal oil (60 vis. at 100 F.;/300 F.) +12% soap.

(2) Low pour coastal oil 35 vis. at 100 F.;/215 F.)+6% soap.

(3) Blend of low pour coastal oil and gas oil (45.2 vis. at 100 F.:/245)'+12% soap.

(4) Secondary butyl sebacate, 12% lithium soap-{4% stabilizer.

(5) z-Ethylhexyl soap+1% stabilizer.

From the above data it will be noted that the greases o! the present invention are much superior to ordinary low temperature greases with respect to evaporation in both the cone and bearing evaporation tests and as stable against bleeding as the other greases. In the plasticity number test, numbers up to and including 2000 are in the free spinning range; irom 2000-10,000 representing free turning and above 10,000 excessive torque or drag.

What is claimed is:

1. A low temperature grease consisting essentially of a major proportion of one or more compounds having the formula COOR1(R) COORz sebacate, 12% lithium carbon radicals; a minor proportion comprising not more than 30% of a soap of a metal selected from the group consisting of alkali and alkaline earth metal and 0.5 to 5% of an amphoteric metal soap as a stabilizer.

2. A low temperature grease according to claim 1 in which R is a polymethylene radical having 8 methylene groups.

3. A low temperature grease composition according to claim 1 in which R1 and Rs are 2- ethylhexyl radicals.

4. A low temperature grease composition according to claim 1 in which R is a polymethylene radical having 8 methylene groups and R1 and R2 are secondary butyl radicals.

5. A low temperature grease comprising at least 65% of a. compound having the formula COORi (R) COOR:

carbon radicals; 6-30% of a soap oi a metal selected from the group consisting of alkali and alkaline earth metal and 0.5 to 5% of an amphoteric metal soap as a stabilizer.

6. A low temperature grease comprising at least of a compound having the formula COOR1(R) COOR:

where R is a bivalent aliphatic hydrocarbon radical; R1 and R: are branched chain hydrocarbon radicals; 12% of a soap 01. a metal selected from the group consisting of alkali and alkaline earth metal and 1% of a compound selected from the class consisting of the oxides, carbonates and soaps of amphoterio metals as a stabilizer.

7. A low temperature grease according to claim 1 in which the soap of a metal is 6-30% of lithium soap of hydrogenated fish oll acids.

8. A low temperature grease composition comprising at least 65% of di-2-ethylhexyl sebacate; 6-30% of a soap of a metal selected from the group consisting of alkali and alkaline earth metal and 0.1 to 5% of an amphoteric metal soap as a stabilizer.

9. A low temperature grease composition comprising at least 65% of the ester isobutyl, 2- ethylhexyl sebacate; 6-30% 01' a soap of a metal selected from the group consisting of alkali and alkaline earth metal and 0.5 to 5% of an amphoteric metal soap as a stabilizer.

JOHN C. ZIMMER. ARNOLD J. MORWAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,993,738 Graves Mar. 12, 1935 2,104,408 Wiezevich Jan. 4, 1938 2,134,736 Reuter Nov. 1, 1938 2,158,096 Werntz May 16, 1939 2,204,601 Kavanagh et a1. June 18, 1940 2,351,280 Morgan I 'June 13, 1944 2,362,767 Morgan 11 Nov. 14, 1944 2,363,513

Farrington et al.- Nov. 28, 1944 

